Metallurgical powder compositions and methods of making and using the same

Abstract

The present invention provides iron-based metallurgical powder compositions and a method of making and using the same. The metallurgical powder compositions of the present invention contain certain amounts of an iron-alloy powder having iron and at least one alloying additive; substantially pure iron powder; and a carbon powder, such as graphite. The metallurgical powder compositions are prepared by admixing the iron-alloy powder with the iron powder and carbon powder. The metallurgical powder compositions thus produce and when formed into metal parts have, for example, improved machinability properties.

What is claimed is:  
     
         1 . A method of making a metallurgical powder composition comprising the steps of: 
 (a) providing an iron-alloy powder comprising iron and at least one alloying additive, wherein the alloying additive is present in an amount of from about 0.01 weight percent to about 7 weight percent and the iron is present in an amount of at least 85 weight percent based on the total weight of the iron-alloy powder; and    (b) admixing with the iron-alloy powder a substantially pure iron powder and carbon to form a metallurgical powder composition, wherein the metallurgical powder composition comprises from about 5 weight percent to about 40 weight percent of the iron-alloy powder, at least 55 percent by weight of the substantially pure iron powder, and at least 0.1 weight percent of the carbon based on the total weight of the metallurgical powder composition.    
     
     
         2 . The method of  claim 1  wherein the alloying additive in the iron-alloy powder is selected from the group consisting of molybdenum, chromium, vanadium, tungsten, and combinations thereof.  
     
     
         3 . The method of  claim 2  wherein the alloying additive is molybdenum.  
     
     
         4 . The method of  claim 3  wherein the molybdenum is present in the iron-alloy powder in an amount of from about 0.1 to about 2.0 weight percent, based on the total weight of the iron-alloy powder.  
     
     
         5 . The method of  claim 1  wherein the metallurgical powder composition further comprises at least one alloying powder.  
     
     
         6 . The method of  claim 5  wherein the alloying powder comprises copper, nickel, or combinations thereof.  
     
     
         7 . The method of  claim 1  wherein the metallurgical powder composition further comprises copper, nickel, graphite, manganese sulfide, or combinations thereof.  
     
     
         8 . The method of  claim 1  wherein the metallurgical powder composition comprises from about 10 weight percent to about 30 weight percent of the iron-alloy powder based on the total weight of the metallurgical powder composition and wherein the iron-alloy powder comprises from about 0.1 weight percent to about 2 weight percent molybdenum based on the total weight of the iron-alloy powder.  
     
     
         9 . The method of  claim 8  wherein the metallurgical powder composition comprises from about 70 weight percent to about 95 weight percent of the substantially pure iron powder, from about 0.1 weight percent to about 3 weight percent carbon, and from about 0.10 to about 3.0 weight percent copper, based on the total weight of the metallurgical powder composition.  
     
     
         10 . An improved metallurgical powder composition comprising: 
 (a) from about 5 weight percent to about 40 weight percent of an iron-molybdenum alloy powder comprising iron and molybdenum, wherein the amount of molybdenum is from about 0.10 weight percent to about 7.0 weight percent and the amount of iron is at least 85 weight percent based on the weight of the iron-molybdenum alloy powder;    (b) at least 55 weight percent of a substantially pure iron powder; and    (c) from about 0.1 weight percent to about 3 weight percent of carbon.    
     
     
         11 . The metallurgical powder composition of  claim 10  wherein the metallurgical composition further comprises at least one alloying powder.  
     
     
         12 . The metallurgical powder composition of  claim 10  wherein the metallurgical composition further comprises nickel, copper, graphite, manganese sulfide, or combinations thereof.  
     
     
         13 . The metallurgical powder composition of  claim 10  wherein the metallurgical powder composition comprises from about 10 weight percent to about 30 weight percent of the iron-molybdenum alloy powder, from about 70 weight percent to about 95 weight percent of the substantially pure iron, from about 0.1 weight percent to about 2 weight percent of the carbon, and from about 0.10 to about 3.0 weight percent copper, based on the total weight of the metallurgical powder composition.  
     
     
         14 . A method of forming a metal part comprising the steps of: 
 (a) providing a metallurgical powder composition comprising a mixture of: 
 (i) from about 5 weight percent to about 40 weight percent, based on the weight of the metallurgical powder composition, of a iron-alloy powder comprising iron and at least one alloying additive, wherein the alloying additive is present in an amount of from about 0.01 weight percent to about 7 weight percent and the iron is present in an amount of at least 85 weight percent, based on the total weight of the iron-alloy powder;  
 (ii) at least 55 weight percent of substantially pure iron powder; and  
 (iii) at least about 0.1 weight percent of carbon; and  
   (b) compacting the metallurgical powder composition at a pressure of at least about 5 tsi to form a metal part.    
     
     
         15 . The method of  claim 14  wherein the alloying additive is molybdenum and is present in the iron-alloy powder in an amount of from about 0.1 to about 3.0 weight percent, based on the total weight of the iron-alloy powder.  
     
     
         16 . The method of  claim 15  further comprising the step of sintering the compacted metal part at a temperature of at least 1900° F. to form a machinable metal sintered part.